Ferenigra is a rare semi-melanic form of the Tau Emperor, where a good deal of the normal orange colour is suffused or even replaced with black. These come from central Europe and are very scarce indeed. Ferenigra is a form for the connoisseur.

The pupae emerge in April. Breeding is very easy. The larvae feed on a variety of trees which include Lime, Hawthorn, Oak, Beech, Willows and Sallows.